What happened
The aircraft was operating under an IFR clearance and was being radar vectored to the ILSS final approach course at 3,000 feet when it experienced an in-flight breakup. At 12:19, the pilot requested destination weather from the center controller, receiving a METAR report of 10 miles visibility with broken cloud layers at 4,000 and 20,000 feet. Shortly after this update, conditions at the destination rapidly deteriorated, characterized by lowering ceilings, heavy rain showers, and strong, gusty winds. A special observation issued five minutes before the accident noted visibility of 2 miles in moderate rain and mist with winds gusting between 14 and 19 knots.
The investigation
The debris path spanned one-quarter mile. The first pieces of wreckage identified were the left wing tip and the outboard half of both the left and right horizontal stabilators. Investigators found that the horizontal stabilators exhibited permanent down deformation at the separation points. Additionally, the wings showed permanent up and down deformation of the spars and other structural elements. Analysis of the fracture surfaces at the separation points for the wings and stabilators indicated they were consistent with structural overload.
Findings
An analysis of weather radar and satellite imagery revealed strong weather echoes near the accident site, including embedded areas of intense to extreme intensity with tops exceeding 33,000 feet. The investigation identified several low-level wind shear layers containing moderate to severe turbulence. While the National Weather Service had issued SIGMETs and AIRMETs for occasional severe turbulence, strong gusty winds, low-level wind shear, and severe rime or mixed icing, there was no record that the pilot requested or received a preflight weather briefing.